During the preparation of cheese types, such as Edam, Jarlsberg and Danbo (all registered trademarks), the prepressing part of the process is decisive for the characteristic texture of the cheese. The above cheese types are compact having uniform, circular fermentation holes caused by carbon dioxide formed during the ripening. Originally the prepressing was performed at the bottom of the cheese vat, in which the curd had been prepared. Subsequent to the final stirring the cheese grains were dragged up to one end of the cheese vat by means of a perforated plate or wall. Thus the cheese grains were separated from the main part of the free-flowing whey. The small, preferably rectangular area holding the cheese grains was then covered by a heavy press screen. At the same time the draining of the whey was started from the opposite end of the vat. The pressure on the resulting cheese block was gradually increased by means of weights evenly distributed on the press screen. After 10-30 min the press screen was removed and the drained cheese block was cut into suitable pieces, which were then conveyed to the next part of the process: forming and final pressing.
This known method is only suitable for the cheese making from small portions of cheese milk (up to approx. 6,000 1). Otherwise the area of the cheese blocks is so large that the free-flowing whey cannot escape during prepressing. This results in texture defects in form of small irregular holes under the rind in the finished cheeses due to the presence of whey with a high concentration of lactose causing fermentation along the rim of the cheese block.
When large cheese vats and closed cheese tanks were introduced prepressing in the vat became impossible and special prepressing vats with perforated plates above the bottom and fixed walls were introduced instead. Subsequent to the final stirring in the cheese vat or tank the whey-and-cheese grain mixture was pumped or dumped into a prepressing vat. During this step air is automatically entrapped in the whey, said air being difficult to remove before the beginning of the prepressing. The air is likely to cause fat oxidation and defects in the cheese. Moreover, air bubbles are retained under or in the perforated bottom plate, said bubbles gradually meandering into the cheese during prepressing.
Since then continuously operating assemblies have been developed, where the cheese is prepressed in columns by means of the weight of its grains; the free-flowing whey is continuously drained off in perforated zones. The problem of entrapped air does, however, still exist, as the comparatively high columns of whey and cheese grain do not offer sufficient escape possibilities.
The Danish patent application 5022/85 discloses a method for the preparation of curd blocks for the preparation of cheeses by removing the whey from the curd. In this method the curd is fed to a draining belt, whereon the resulting curd body is subjected to stepwise forward movement while the whey is removed. The curd is fed to the draining belt via an antechamber the bottom of which is formed by the draining belt. This antechamber is separated from the following part by means of a partition forming a small gap opposite the draining belt. As a result the curd is fed to the draining belt under overpressure initiating the separation of the whey. After having passed the partition the curd or cheese body formed by the cheese grains expands. While still being conveyed by the draining belt the curd body is subjected to prepressing means giving it the desired thickness. Simultaneously the desired width is determined by adjustable side walls. Then the cheese body is cut into blocks of predetermined size.